The present invention relates to a method for high-speed searching in an optical recording/reproducing apparatus, particularly to a method for finding out a target track by of transforming the number of the tracks to be moved in a compact disk to a value of time by velocity.
An optical recording/reproducing apparatus, in general, refers to a compact disk player which has been widely propagated, a video disk player and compact disk ROM(namely, CD-ROM) which is an apparatus for recording data.
Within such an optical recording/reproducing apparatus several servo systems are employed to provide the reading-out information from the disk. The several servo systems include a tracking servo for tracking, a focusing servo, a sled servo(or radial servo) for transferring an optical apparatus into the circumference of a disk, and a rotary servo for rotating a disk.
FIG. 1 shows a block diagram of the optical recording/reproducing apparatus as described above.
The apparatus in FIG. 1 consists of a pick-up unit 12 for picking up recording information on a disk 10 a radio-frequency amplifier 14 for amplifying the signal picked up by the pick-up unit 12, a signal processing unit 16 for filtering the pulse of an output signal from the radio-frequency amplifier 14 and for demodulating with eight to fourteen modulation (EFM), a servo unit 18 for inputting the output signal of the radio-frequency amplifier 14 and the EFM waveform reshaping signal of the signal processing unit 16 and for outputting a control signal for the tracking, focusing and the sled servo, and a disk motor driving control signal, a sled motor driving unit 22 for driving the sled motor of the pick-up unit 12 by inputting the sled servo control signal generated from the servo unit 18, an actuator driving unit 28 for driving a tracking and focusing actuator of the pick-up unit 12 by inputting the tracking and focusing servo control signals generated from the servo unit 18, a spindle motor driving unit 24 for driving a disk spindle motor 26 to rotate the disk by inputting a control signal for driving the spindle motor, generated from the servo unit 18.
A detailed description will be given not to the general system of the optical recording/reproducing apparatus as shown in FIG. 1, but to the pick-up unit 12, the servo unit 18 and sled motor driver 22, which the present invention concerns.
In the system as shown in FIG. 1, the pick-up unit 12 includes a tracking actuator, a focusing actuator, and a sled motor for moving optical tools such as a lens in the arrow direction 31. And the servo unit 18 detects a tracking error and a focusing error from the output signal from the radio-frequency amplifier 14 and then outputs a tracking servo signal and a focusing servo signal, and also outputs a sled servo signal according to the tracking signal or according to a search-controlling signal of a controller 21.
A conventional search unit as shown in FIG. 2, can detect the optical quantity of the ray, by means of photo-diodes (A-F), reflected from the disk 7. The detected signal from photo-diodes (A-F) is applied to an EFM processor through a high frequency amplifier (not shown herein), and analyzed to EFM data. Also in the system, an error detecting signal generated from the photo-diodes (E, F) is applied to the E-F amplifier (2), and amplified.
In a track servo unit 3 receiving the error detecting signal from the E-F amplifier 2, track pick-up operation is carried out owing to the generation of a lens driving signal of the pick-up unit 1. When the drift range a lens of the pick-up unit becomes the maximum value, the output signal of the track servo unit 3 is applied to the sled servo unit 4.
The sled servo unit 4 receiving the output signal from the track servo unit 3 allows the pick-up point to be moved by driving the sled motor of the pick-up unit 1. In order to search a position by measuring the number of tracks moved, the track error signal of the E-F amplifier 2 is applied to the waveform reshaping unit 5 and a square-wave is generated therefrom.
A digital signal processing unit 6, hereinafter called as DSPU) receiving the square-wave, counts the number of the square-waves and measures the target tracks. The track signal measured by counting in the DSPU 6 is applied to the sled servo unit 5 and drives the sled motor of the pick-up unit 1 by means of the track signal, and so resultedly a predetermined position of the target track can be searched.
However, the search unit described above as the prior art has a drawback that, if a beam does not pass over a pit on the disk, the number of tracks can not be counted, and another drawback is that, if the sled motor operates at high speed, the tracking error signal can not be generated.